WSJ: Justices fired a barrage of questions at the government’s lawyer, Solicitor General Donald Verrilli.

The Supreme Court’s five conservative justices on Tuesday sharply challenged the Obama administration’s arguments for the health-care law, with Justice Anthony Kennedy saying the government has a “very heavy burden of justification” for the law’s requirement that people carry health insurance or pay a penalty.

The conservative justices fired a barrage of questions at the government’s lawyer, Solicitor General Donald Verrilli, asking him to explain why the Constitution authorizes Congress to enact the insurance mandate.

As in lower courts, the federal government on Tuesday struggled to outline a workable principle that would limit the ability of Congress to require people to make other kinds of purchases in the future. Chief Justice John Roberts said that if the court approved of the mandate, it may be hard to set limits.